We received the following in an email from John Goff, lead forecaster at the Burlington, Vermont National Weather Service office:

“Couldn’t help but notice the apparent large ice eddies up in the Gulf of Saint Lawrence this afternoon (3/6) per the TERRA MODIS noon overpass (250m res). I thought that initially these were eddy/small-scale cloud vortices we sometimes see up there, but upon looping the GOES visible imagery on my AWIPS workstation it’s fairly obvious these are not clouds, but ice structures.”

Thanks John for the heads-up on this very interesting example! McIDAS images of 1-km resolution GOES-13 0.63 Âµm visible channel data (above; click image to play animation) showed the development and motion of the ice eddies on 06 March 2012. Note how many of the ice floe structures began to move toward the northeast by the end of the day, due to increasing southwesterly surface winds across the region.

A comparison of AWIPS images of 1-km resolution MODIS 0.65 Âµm visible channel data and the corresponding MODIS false-color Red/Green/Blue (RGB) image (below) demonstrated the value of using RGB imagery to aid in the discrimination between snow/ice (which appeared as varying shades of red in the false-color RGB image) and supercooled water droplet clouds (which appeared as the brighter white to cyan features on the RGB image).

An AWIPS image of the 1-km resolution POES AVHRR Sea Surface Temperature (SST) product at 18:55 UTC (below) indicated that SST values over the open waters were in the 30-31Âº F range (blue color enhancement), while the ice features exhibited colder values in the 23-25Âº F range (violet color enhancement).

POES AVHRR Sea Surface Temperature product

Finally, a comparison of 250-meter resolution MODIS true color and false color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below) showed a closer view of the ice eddies, and again demonstrated the value of using various RGB image combinations to discriminate between snow/ice (cyan in the false-color image) and supercooled water droplet low cloud features (white on the true-color image).

MODIS true-color and false-color Red/Green/Blue (RGB) images

CIMSS participation in GOES-R Proving Ground activities includes making a variety of POES AVHRR and MODIS images and products available for National Weather Service forecast offices to add to their local AWIPS workstations. Currently there are 51 NWS offices receiving MODIS imagery and products from CIMSS.

McIDAS images of GOES-15 10.7 Âµm IR channel data (above; click image to play animation) showed the cold cloud tops (some -60Âº C and colder, red color enhancement) associated with numerous large thunderstorms that moved across the northern Hawaiian Islands of Kauai and Oahu during the 04 March – 06 March 2012 period. Storm total rainfall amounts were as high as 35.97 inches at Hanalei on Kauai, and 15.64 inches at Punaluu Stream on Oahu. Lihue on Kauai set a new daily record rainfall amount with 8.64 inches falling on 05 March.

As one of the largest thunderstorm complexes was approaching the island of Kauai from the southwest around 03 UTC on 06 March (5 pm local time on 05 March), a comparison of a 1-km resolution NOAA-15 AVHRR 10.8 Âµm IR channel image to the corresponding 4-km resolution GOES-15 10.7 Âµm IR channel image (below) demonstrated the advantage of higher spatial resolution for identifying the location of colder cloud top IR brightness temperatures associated with convective overshooting tops. Southwest of Kauai the coldest IR temperature on the AVHRR image was -70Âº C, compared to -62Âº C on the GOES-15 image.

GOES-15 6.5 Âµm water vapor channel images with water vapor Atmospheric Motion Vector (AMV) winds from the CIMSS Tropical Cyclones site (above) showed that a well-defined trough of low pressure was located to the northwest of the Hawaiian Islands during the 05 March – 06 March period.

Juxtaposed beneath the strong upper-tropospheric divergence was strong lower-tropospheric convergence in the vicinity of the stationary front / wind shear axis, as seen in GOES-15 10.7 Âµm IR images with contours of IR satellite wind derived 850-925 hPa convergence (below). This created a favorable environment for upward vertical motion, with plenty of deep moisture to fuel the development of the strong thunderstorms.

The powerful mid-latitude cyclone that was responsible for the widespread outbreak of severe weather across parts of the eastern US on 02 March 2012 spawned a southward surge of cold air (OPC surface analyses) that traversed the Gulf of Mexico, crossed the mountainous terrain of far southern Mexico, and emerged across the Pacific Ocean as a strong gap wind event known as a Tehuano wind. AWIPS images showing METAR surface reports, Tropical surface analyses, and a pass of ASCAT scatterometer surface winds (above) showed that there was blowing sand reported at Veracruz(station identifier MMVR), with wind gusts to 45 knos at Minatitlan(station identifier MMMT) and 35 knots at Ixtepec(station identifier MMIT).

McIDAS images of GOES-13 0.63 Âµm visible channel data from 04 March 2012(below; click image to play animation) showed the cloud arc that marked the leading edge of the Tehuano wind, and also showed the hazy signature of blowing dust that was being lofted southward across the Pacific coast and over the waters of the Gulf of Tehuantepec (hence the name â€œTehuantepecerâ€œ given to this type of strong wind event).

One of the largest severe weather outbreaks on record for the month of March occurred from the Ohio River Valley to the Gulf Coast states on 02 March 2012. This outbreak produced dozens of tornadoes, more than 400 hail reports (as large as 4.25 inches in diameter in Kentucky), and over 200 reports of severe damaging winds (SPC storm reports) — and was responsible for more than 30 fatalities. Focusing on one of the hardest-hit regions (from southern Indiana into Kentucky), a composite of the total cumulative SPC hail, severe damaging wind gust, and tornado reports are overlaid on an AWIPS image of 1-km resolution POES AVHRR 10.8 Âµm IR data (above).

4-km resolution GOES-13 10.7 Âµm IR images with overlays of corresponding SPC storm reports (below; click image to play animation) showed that during the 16:25 to 23:45 UTC period a number of cold overshooting cloud tops (IR brightness temperatures as cold as -70Âº C, darker black color enhancement, at 19:45 UTC), enhanced-V signatures, and cold-warm thermal couplets could be seen. For the large supercell thunderstorm that produced the tornado/tornadoes that did EF4 damage in Henryville in far southern Indiana after about 20:11 UTC, we can see that it exhibited fairly well-defined enhanced-V and/or cold/warm thermal couplet cloud top sinatures as it moved eastward across southern Indiana during the hour or two leading up to the tornadoes. Henryville is located approximately halfway between Seymour, Indiana (station identifier KSER) and Louisville, Kentucky (station identifier KSDF).

About an hour prior to the Henryville tornado, a comparison of 1-km resolution MODIS 0.65 Âµm visible channel and 11.0 Âµm IR channel images at 19:10 UTC (below) displayed a large thunderstorm over far southern Indiana, with overshooting top shadows seen on the visible image and an enhanced-V with a distinct cold/warm thermal couplet cloud top signature on the IR image.

MODIS 0.65 Âµm visible chaneel + 11.0 Âµm IR channel images

In a comparison of the 19:10 UTC 1-km resolution MODIS 11.0 Âµm IR image with the correspondng 4-km resolution GOES-13 10.7 Âµm IR image (below), the advantage of improved spatial resolution is immediately obvious in terms of being able to identify storm-top severe storm signatures such as the enhanced-V or the cold/warm thermal couplet (Note: the spatial resolution of IR imagery on the next-generation ABI instrument on GOES-R will be 2 km). The coldest cloud-top IR brightness temperature on the MODIS image was -76Âº C, compared to -67Âº C on the GOES-13 image. Also evident is the northwestward “parallax shift” on the GOES-13 IR image, due to the large viewing angle from that particular geostationary satellite located over the Equator at 75Âº West longitude; a more accurate placement of the storm top features is seen using imagery from polar-orbiting satellites that fly more directly overhead.

1-km MODIS 11.0 Âµm IR image + 4-km GOES-13 10.7 Âµm IR image

A similar comparison between the 19:44 UTC 1-km resolution POES AVHRR 10.8 Âµm IR image with the corresponding 4-km resolution GOES-13 10.7 Âµm IR image (below) again demonstrated the easier identification of important storm-top signatures with improved spatial resolution data. These images were about 20-30 minutes before the Henryville and Marysville tornadoes in far southern Indiana.

1-km POES AVHRR 10.8 Âµm IR image + 4-km GOES-13 10.7 Âµm IR image

Many of the supercell thunderstorms exhibited unusally fast forward motion speeds (as fast as 70-80 mph), due to the approach of a strong 140-knot core upper-level jet streak. A 1-km resolution MODIS 6.7 Âµm water vapor channel image with an overlay of NAM maximum wind speeds is shown below — strong divergence aloft within the left exit region of this upper-level jet streak helped to promote an environment supportive of strong vertical ascent.

MODIS 6.7 Âµm water vapor channel image + NAM maximum wind speeds

From a larger synoptic-scale point of view, 10-km resolution GOES-13 sounder Lifted Index (LI) derived product imagery (below; click image to play animation) did begin to show a trend of destabilization early in the day within the warm sector of the mid-latitude cyclone, before extensive cloud cover prevented the subsequent retrieval of GOES sounder-based products.

Blended Total Precipitable Water product (click image to play animation)

In terms of moisture, the Blended Total Precipitable Water product (above; click image to play animation) showed that TPW values in excess of 25 mm (or 1.0 inch) were being drawn northward within the warm sector of the cyclone. These TPW values were near or even in excess of 200 percent above normal for many areas for this early in the season (below; click image to play animation).

Percent of Normal Blended Total Precipitable Water (click image to play animation)

———————————- 10 March Update ——————————

Before (01 March) and after (10 March) MODIS true-color RGB images

A comparison of before (01 March 2012) and after (10 March 2012) 250-meter resolution MODIS true-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) revealed the southwest-to-northeast oriented tornado damage path from the Henryville, Indiana EF4 tornado.